Patriarch Nikon
In the mid-17th century, the reform leader was the patriarch of Moscow (the spiritual leader of the Russian Orthodox Church), a monk called Nikon. He and his followers made schools that spoke Latin, Greek, and Church Slavonic (ritual language of the Russian Orthodox church). There were churches that were built in the Byzantine style.
The reformation required for Russian priests to make the sign of the cross with three fingers instead of two which was common with Orthodox priests of different lands. Conservatives took this change as a symbol that the church leadership had turned on its traditional ways. Nikon had a huge resistance even with the help of the tsar. A group of conservative monks with the aid of 90 cannons held against a tsarist reformation force in the fortified Solovestskii monastery for seven years.